1. Technical Field
This invention generally relates to computer systems, and more specifically relates to apparatus and methods for relocating hardware context structures in a computer system without halting the operation of the computer system, adapter hardware, or program applications dependent on the operation of the adapter hardware.
2. Background Art
Since the dawn of the computer age, computer systems have evolved into extremely sophisticated devices that may be found in many different settings. Computer systems typically include a combination of hardware (e.g., semiconductors, circuit boards, etc.) and software (e.g., computer programs). As advances in semiconductor processing and computer architecture push the performance of the computer hardware higher, more sophisticated computer software has evolved to take advantage of the higher performance of the hardware, resulting in computer systems today that are much more powerful than just a few years ago.
Advances in computer architecture are increasing system performance by using hardware state machines to implement low-level communications functions, such as bus link and transport protocol. By implementing these functions in hardware, the software is relieved of the burden of performing these functions. Because these functions may be implemented in hardware much more quickly than in software, the result is an overall improvement in system performance.
The use of virtual connections between software applications allows those applications to communicate in an efficient, predefined manner. As the number of software applications that communicate via virtual connections increases, the number of virtual connections that a computer system must support goes up dramatically. Hardware in today's computer systems needs to support a large number of virtual connections. Each virtual connection has a critical set of information that is necessary to control the transfer of data. This critical set of information is commonly referred to as “connection context.” As the number of virtual connections grows, hardware state machines that perform the low-level communication functions must maintain fast accessibility to a large number of connection contexts. This can be done by maintaining the context information within an application-specific integrated circuit (ASIC), but the limitations in size of memory on an ASIC inherently limits the number of connection contexts that can be stored in the ASIC. In the alternative, a dedicated memory for storing the connection contexts could be connected to the ASIC. While a dedicated memory generally allows for more storage capacity than memory on an ASIC, it is still limited to the capacity of the memory components used. Still another way to store a large number of connection contexts is to provide a separate memory subsystem that is accessible to the ASIC and other processes. In a typical computing system, the connection contexts would be stored in a specified area of main memory. This latter approach is the most flexible of the three because the amount of memory used for connection contexts is limited only by the total system memory.
Infiniband is a communication protocol that supports bidirectional communication using queue pairs to provide virtual connections. One Infiniband host channel adapter typically supports 16,384 queue pairs. Each queue pair may require 512 bytes of context, resulting in the need for 8 megabytes (MB) of memory for context alone. In addition, the architected number of queue pairs in Infiniband is 16M. Assuming 512 bytes of context per queue pair, a host channel adapter implementing all architected queue pairs would require 8 gigabytes (GB) of memory for context.
In the prior art, there is no known way to move hardware state machine context information from one block of main memory to a different block of main memory without shutting down and restarting all of the virtual connections. For example, referring to FIG. 3, a prior art method 300 for relocating hardware context information in memory begins by shutting down all virtual connections (step 310). Next, the hardware context structure is copied from the original context memory to the new context memory (step 320). Once the copy is complete, all virtual connections have to be re-established (step 330). Shutting down all connections makes the computer system unavailable until the connections are restarted. Furthermore, there is significant overhead in shutting down and restarting all connections. Without a way to move hardware context structures without shutting down the virtual connections, the computer industry will continue to suffer from inefficient methods of moving hardware context structures in memory.